Transmission speed control method, mobile station, and radio line control station

ABSTRACT

The present invention relates to a transmission rate control method for controlling a transmission rate of user data to be transmitted via an uplink by a mobile station. A radio network controller notifies an initial maximum allowable transmission rate of the user data to the mobile station, when a serving cell of the mobile station is to be changed. The mobile station increases the transmission rate of the user data up to the initial maximum allowable transmission rate notified from the radio network controller automatically, while the serving cell is being changed. The mobile station increases the transmission rate of the user data up to a maximum allowable transmission rate in the changed serving cell of the mobile station automatically, after the serving cell has been changed.

TECHNICAL FIELD

The present invention relates to a transmission rate control method, amobile station and a radio network controller which control atransmission rate of user data to be transmitted via an uplink by amobile station.

BACKGROUND ART

In a conventional mobile communication system, in an uplink from amobile station UE to a radio base station Node B, a radio networkcontroller RNC is configured to determine a transmission rate of adedicated channel, in consideration of radio resources of the radio basestation NodeB, an interference volume in an uplink, transmission powerof the mobile station UE, transmission processing performance of themobile station UE, a transmission rate required for an upperapplication, and the like, and to notify the determined transmissionrate of the dedicated channel by a message of a layer-3 (Radio ResourceControl Layer) to both of the mobile station UE and the radio basestation Node B.

Here, the radio network controller RNC is provided at an upper level ofthe radio base station Node B, and is an apparatus configured to controlthe radio base station Node B and the mobile station UE.

In general, data communications often cause burst traffic compared withvoice communications or TV communications. Therefore, it is preferablethat a transmission rate of a channel used for the data communicationsis changed fast.

However, as shown in FIG. 1, the radio network controller RNC integrallycontrols a plurality of radio base stations Node B in general.Therefore, in the conventional mobile communication system, there hasbeen a problem that it is difficult to perform fast control for changingof the transmission rate of channel (for example, per approximately 1through 100 ms), due to processing load, processing delay, or the like.

In addition, in the conventional mobile communication system, there hasbeen also a problem that costs for implementing an apparatus and foroperating a network are substantially increased even if the fast controlfor changing of the transmission rate of the channel can be performed.

Therefore, in the conventional mobile communication system, control forchanging of the transmission rate of the channel is generally performedon the order from a few hundred ms to a few seconds.

Accordingly, in the conventional mobile communication system, when burstdata transmission is performed as shown in FIG. 2( a), the data aretransmitted by accepting low-speed, high-delay, and low-transmissionefficiency as shown in FIG. 2( b), or, as shown in FIG. 2( c), byreserving radio resources for high-speed communications to accept thatradio bandwidth resources in an unoccupied state and hardware resourcesin the radio base station Node B are wasted.

It should be noted that both of the above-described radio bandwidthresources and hardware resources are applied to the vertical radioresources in FIGS. 2( a) and 2(c).

Therefore, the 3rd Generation Partnership Project (3GPP) and the 3rdGeneration Partnership Project 2 (3GPP2), which are internationalstandardization organizations of the third generation mobilecommunication system, have discussed a method for controlling radioresources at high speed in a layer-1 and a media access control (MAC)sub-layer (a layer-2) between the radio base station Node B and themobile station UE, so as to utilize the radio resources effectively.Such discussions or discussed functions will be hereinafter referred toas “Enhanced Uplink (EUL)”.

Radio resource control methods that have been discussed in the “EnhancedUplink” can be broadly categorized into three as follows. The radioresource control methods will be briefly described below.

First, a radio resource control method that is referred to as “Time &Rate Control” has been discussed.

In such a radio resource control method, a radio base station Node Bdetermines a mobile station UE which can transmit user data and atransmission rate of user data of the mobile station UE per apredetermined timing, so as to signal information relating to a mobilestation ID as well as the transmission rate of user data (or a maximumallowable transmission rate of user data).

The mobile station UE that is designated by the radio base station NodeB transmits user data at the designated timing and the transmission rate(or within a range of the maximum allowable transmission rate).

Second, a radio resource control method that is referred to as “RateControl per UE” has been discussed.

In such a radio resource control method, if there is user data thatshould be transmitted to the radio base station Node B, each mobilestation UE can transmit the user data. However, the maximum allowabletransmission rate of the user data, which is determined by the radiobase station Node B and signaled to each mobile station UE for eachtransmission frame or each of a plurality of transmission frames, isused.

Here, when the maximum allowable transmission rate is signaled, theradio base station Node B signals the maximum allowable transmissionrate itself, or a relative value thereof (for example, binary of an “Upcommand” and a “Down command”), at this timing.

Third, a radio resource control method that is referred to as “RateControl per Cell” has been discussed.

In such a radio resource control method, a radio base station Node Bsignals a transmission rate of user data, which is common among mobilestations UE in communication, or information needed to calculate thetransmission rate, and each mobile station UE determines a transmissionrate of user data based on the received information.

Ideally, the “Time & Rate Control”, and the “Rate Control per UE” can bethe best control methods for improving radio capacity in an uplink.However, a transmission rate of user data has to be granted after datavolume stored in buffers of the mobile station UE, transmission power inthe mobile station UE, or the like are grasped. Therefore, there hasbeen a problem that control load is increased by the radio base stationNode B.

In addition, in these radio resource control methods, there has been aproblem that overhead becomes larger by exchanges of control signals.

On the other hand, in the “Rate Control per Cell”, there is an advantagein that control load by the radio base station Node B is small since theradio base station Node B signals information which is common in cells,and each mobile station UE autonomously seeks the transmission rate ofuser data based on the received information.

However, the radio base station Node B has to be configured in such amanner that the user data in the uplink from any mobile station UE canbe received. Therefore, there has been a problem that an apparatus sizeof radio base station Node B becomes large to effectively utilize theradio capacity of the uplink.

Accordingly, there has been proposed, for example, a scheme (Autonomousramping method) that the mobile station UE increases the transmissionrate of user data from a pre-notified initial transmission rate inaccordance with predetermined rules so that excessive allocation ofradio capacity by the radio base station Node B can be prevented,thereby preventing increase of the apparatus size of radio base stationNode B, as described in Non-patent Document 1.

In such a scheme, a radio base station Node B determines a maximumallowable transmission rate based on hardware resources and radiobandwidth resources (for example, an interference volume in an uplink)in each sector, so as to control the transmission rate of user data incommunicating mobile stations UE. Detailed descriptions of a controlscheme based on hardware resources and a control scheme based on aninterference volume in an uplink will be given below.

In the control scheme based on the hardware resources, a radio basestation Node B is configured to signal a maximum allowable transmissionrate to a mobile station UE connected to a sector under the controlthereof.

The radio base station Node B lowers the maximum allowable transmissionrate so as to avoid shortage of the hardware resources when thetransmission rate of user data in the mobile station UE connected to thesector under the control thereof is increased and the hardware resourcesare insufficient.

On the other hand, the radio base station Node B again increases themaximum allowable transmission rate when the space of the hardwareresources become larger at a time of completion of user datatransmission in the mobile station UE connected to the sector under thecontrol thereof, or the like.

In addition, in the control scheme based on the interference volume inthe uplink, a radio base station Node B is configured to signal amaximum allowable transmission rate to a mobile station UE connected toa sector under the control thereof.

When the transmission rate of user data in the mobile station UEconnected to the sector under the control of a radio base station Node Bincreases and a measured interference volume (for example, a measurednoise rise) in the uplink exceeds an allowable value (for example, amaximum allowable noise rise), the radio base station Node B lowers themaximum allowable transmission rate so that the interference volume inthe uplink can be within a range of the allowable value (see, FIG. 3).

On the other hand, when the interference volume (for example, the noiserise) in the uplink is within a range of the allowable value (forexample, the maximum allowable noise rise), thereby having a space, atthe time of completion of user data transmission in the mobile stationUE connected to the sector under the control of the radio base stationNode B, or the like, the radio base station Node B again increases themaximum allowable transmission rate (see, FIG. 3).

As for the enhanced uplink, there exists a concept of a serving cell (ora serving cell set). FIG. 4 shows an example of a channel connectionconfiguration in the mobile communication system to which enhanceduplink is applied.

Here, in terms of the enhanced uplink, a channel for transmitting userdata by using the HARQ processing or the scheduling processing isdefined as an Enhanced Dedicated Physical Channel (E-DPCH). A channelfor transmitting uplink user data is defined as an Enhanced DedicatedPhysical Data Channel (E-DPDCH), and a channel for transmitting uplinkcontrol data is defined as an Enhanced Dedicated Physical ControlChannel (E-DPCCH).

In the mobile communication system, not only the E-DPCH but also aconventional Dedicated Physical Channel (DPCH) is also transmitted. Itis assumed that control information on a layer 3 between the corenetwork and the mobile station UE is transmitted on the DPCH.

In addition, in the mobile communication system, an Absolute GrantChannel (AGCH) transmits the maximum allowable transmission rate of theuplink user data.

The mobile station UE always receives the absolute grant channel (AGCH)that is always transmitted from only one cell. Here, a cell transmittingthe AGCH that the mobile station UE should receive is called a “servingcell” of the mobile station UE, and cells belonging to the same radiobase station NodeB as the serving cell are called a “serving cell set”of the mobile station UE.

Since the serving cell controls the transmission rate of the uplink userdata in the mobile station UE, the radio network controller RNCgenerally takes control such that a cell having the strongest electricfield strength in downlink or uplink would become a serving cell. Here,it is called “serving cell change” that a serving cell of a mobilestation is changed.

In the conventional mobile communication system, when resources suitablefor the transmission rate of user data transmitted from the mobilestation UE which performs the cell change are not allocated to adestination cell in the cell change, the cell change is not performedsmoothly.

Accordingly, in such case, the destination cell lowers the signaledmaximum allowable transmission rate to have some margin in theresources, and the resources are secured for the mobile station UE.However, there is a problem that all the user data that have beentransmitted by that time may be received as errors.

More specifically, in the conventional mobile communication system,there is a problem that significant deterioration in communicationquality may occur, since the radio base station NodeB including thedestination cell in the cell change cannot allocate the resources to themobile station in which the cell change is to be performed.

-   (Non-patent Document 1) 3GPP TSG-RAN R1-040773

DISCLOSURE OF THE INVENTION

The present invention has been made considering the problems, and itsobject is to provide a transmission rate control method, a mobilestation and a radio network controller which can prevent significantdeterioration in communication quality attributable to the shortage ofresource allocation in a destination cell, even when cell change isperformed.

A first aspect of the present invention is summarized as a transmissionrate control method for controlling a transmission rate of user data tobe transmitted via an uplink by a mobile station, the method comprisingthe steps of: notifying, at a radio network controller, an initialmaximum allowable transmission rate of the user data to the mobilestation, when a serving cell of the mobile station is to be changed;increasing, at the mobile station, the transmission rate of the userdata up to the initial maximum allowable transmission rate notified fromthe radio network controller automatically, while the serving cell isbeing changed; and increasing, at the mobile station, the transmissionrate of the user data up to a maximum allowable transmission rate in thechanged serving cell of the mobile station automatically, after theserving cell has been changed.

In the first aspect of the present invention, a transmission ratecontrol method may comprise the step of: signaling, at the changedserving cell of the mobile station, the maximum allowable transmissionrate in the changed serving cell of the mobile station to the mobilestation; and the mobile station may increase the transmission rate ofthe user data up to the signaled maximum allowable transmission rateautomatically, after the serving cell has been changed.

In the first aspect of the present invention, the radio networkcontroller may notify the maximum allowable transmission rate in thechanged serving cell of the mobile station to the mobile station, withusing a layer-3 message; and the mobile station may increase thetransmission rate of the user data up to the notified maximum allowabletransmission rate automatically, after the serving cell has beenchanged.

A second aspect of the present invention is summarized as a mobilestation which transmits user data via an uplink, comprising: an initialmaximum allowable transmission rate receiving unit configured to receivean initial maximum allowable transmission rate of the user data notifiedby a radio network controller, when a serving cell of the mobile stationis to be changed; and a transmission rate control unit configured toincrease a transmission rate of the user data up to the initial maximumallowable transmission rate notified from the radio network controllerautomatically, while the serving cell is being changed; and to increasethe transmission rate of the user data up to a maximum allowabletransmission rate in the changed serving cell of the mobile stationautomatically, after the serving cell has been changed.

In the second aspect of the present invention, the mobile station maycomprise a maximum allowable transmission rate receiving unit configuredto receive the maximum allowable transmission rate in the changedserving cell of the mobile station signaled by the changed serving cellof the mobile station; and the transmission rate control unit may beconfigured to increase the transmission rate of the user data up to thereceived maximum allowable transmission rate automatically.

In the second aspect of the present invention, the mobile station maycomprise a maximum allowable transmission rate receiving unit configuredto receive the maximum allowable transmission rate in the changedserving cell of the mobile station notified by the radio networkcontroller; and the transmission rate control unit may be configured toincrease the transmission rate of the user data up to the receivedmaximum allowable transmission rate automatically.

A third aspect of the present invention is summarized as a radio networkcontroller which controls a transmission rate of user data to betransmitted via an uplink by a mobile station, comprising: an initialmaximum allowable transmission rate notifying unit configured to notifyan initial maximum allowable transmission rate of the user data to themobile station, when a serving cell of the mobile station is to bechanged.

In the third aspect of the present invention, the radio networkcontroller may comprise a maximum allowable transmission rate configuredto notify the maximum allowable transmission rate in the changed servingcell of the mobile station to the mobile station, with using a layer-3message, after the serving cell has been changed.

A fourth aspect of the present invention is summarized as a transmissionrate control method for controlling a transmission rate of user data tobe transmitted via an uplink by a mobile station, the method comprisingthe steps of: notifying, at a radio network controller, an initialmaximum allowable transmission rate of the user data to the mobilestation, when a serving cell of the mobile station is to be changed;determining, at the mobile station, the transmission rate of the userdata based on the initial maximum allowable transmission rate notifiedfrom the radio network controller, while the serving cell is beingchanged; and determining, at the mobile station, the transmission rateof the user data based on a maximum allowable transmission rate in thechanged serving cell of the mobile station, after the serving cell hasbeen changed.

In the fourth aspect of the present invention, a transmission ratecontrol method may comprise the step of: signaling, at the changedserving cell of the mobile station, the maximum allowable transmissionrate in the changed serving cell of the mobile station to the mobilestation; and the mobile station may determine the transmission rate ofthe user data based on the signaled maximum allowable transmission rate,after the serving cell has been changed.

In the fourth aspect of the present invention, the radio networkcontroller may notify the maximum allowable transmission rate in thechanged serving cell of the mobile station to the mobile station, withusing a layer-3 message; and the mobile station may determine thetransmission rate of the user data based on the notified maximumallowable transmission rate, after the serving cell has been changed.

A fifth aspect of the present invention is summarized as a mobilestation which transmits user data via an uplink, comprising: an initialmaximum allowable transmission rate receiving unit configured to receivean initial maximum allowable transmission rate of the user data notifiedby a radio network controller, when a serving cell of the mobile stationis to be changed; and a transmission rate control unit configured todetermine a transmission rate of the user data based on the initialmaximum allowable transmission rate notified from the radio networkcontroller, while the serving cell is being changed; and to determinethe transmission rate of the user data based on a maximum allowabletransmission rate in the changed serving cell of the mobile station,after the serving cell has been changed.

In the fifth aspect of the present invention, the mobile station maycomprise a maximum allowable transmission rate receiving unit configuredto receive the maximum allowable transmission rate in the changedserving cell of the mobile station signaled by the changed serving cellof the mobile station; and the transmission rate control unit may beconfigured to determine the transmission rate of the user data based onthe received maximum allowable transmission rate.

In the fifth aspect of the present invention, the mobile station maycomprise a maximum allowable transmission rate receiving unit configuredto receive the maximum allowable transmission rate in the changedserving cell of the mobile station notified by the radio networkcontroller; and the transmission rate control unit may be configured todetermine the transmission rate of the user data based on the receivedmaximum allowable transmission rate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an entire configuration of a general mobilecommunication system.

FIGS. 2( a) to 2(c) are graphs illustrating operations at the time ofburst data transmission in a conventional mobile communication system.

FIG. 3 is a graph illustrating operations at the time of controllingtransmission rate in an uplink in the conventional mobile communicationsystem.

FIG. 4 is a diagram showing a channel connection configuration in amobile communication system to which conventional enhanced uplink isapplied.

FIG. 5 is a functional block diagram of a mobile station of a mobilecommunication system according to an embodiment of the presentinvention.

FIG. 6 is a functional block diagram of a baseband signal processingsection in a mobile station of the mobile communication system accordingto the embodiment of the invention.

FIG. 7 is a functional block diagram of a MAC-e processing section ofthe baseband signal processing section in a mobile station of the mobilecommunication system according to the embodiment of the invention.

FIG. 8 is a functional block diagram of a radio base station of themobile communication system according to the embodiment of theinvention.

FIG. 9 is a functional block diagram of a baseband signal processingsection in a radio base station of the mobile communication systemaccording to an embodiment of the invention.

FIG. 10 is a functional block diagram of a MAC-e and Layer 1 processingsection (configuration for uplink) of the baseband signal processingsection of a radio base station of the mobile communication systemaccording to the embodiment of the invention.

FIG. 11 is a functional block diagram of a MAC-e functional section ofthe MAC-e and Layer 1 processing section (configuration for uplink) inthe baseband signal processing section in a radio base station of themobile communication system according to the embodiment of the presentinvention.

FIG. 12 is a functional block diagram of a radio network controller ofthe mobile communication system according to the embodiment of thepresent invention.

FIG. 13 is a sequence diagram showing an operation of the mobilecommunication system according to an embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

(Configuration of Mobile Communication System According to FirstEmbodiment of the Present Invention)

A description will be given of a configuration of a mobile communicationsystem according to a first embodiment of the present invention withreference to FIGS. 5 to 12.

It should be noted that, as shown in FIG. 1, the mobile communicationsystem according to this embodiment is provided with a plurality ofradio base stations Node B #1 to Node B #5 and a radio networkcontroller RNC.

The mobile communication system according to the present embodiment isconfigured to control a transmission rate of user data transmitted viaan uplink by a mobile station UE.

In addition, in the mobile communication system according to thisembodiment, a “High Speed Downlink Packet Access (HSDPA)” is used in adownlink, and an “Enhanced Uplink (EUL)” is used in an uplink.

It should be noted that in both of the HSDPA and the EUL, retransmissioncontrol (N process stop and wait) shall be performed by a “HybridAutomatic Repeat Request (HARQ)”.

Therefore, in an uplink, an “Enhanced Dedicated Physical Channel(E-DPCH)” configured of an “Enhanced Dedicated Physical Data Channel(E-DPDCH)” and an “Enhanced Dedicated Physical Control Channel(E-DPCCH)”, and a “Dedicated Physical Channel (DPCH)” configured of a“Dedicated Physical Date Channel (DPDCH)” and a “Dedicated PhysicalControl Channel (DPCCH)” are used.

Here, the E-DPCCH transmits control data for the EUL such as atransmission format number for defining a transmission format(transmission block size, or the like) of the EDPDCH, HARQ relatedinformation (the number of retransmission, or the like), and schedulingrelated information (transmission power, buffer residence-volume, or thelike in the mobile station UE).

In addition, the E-DPDCH is paired with the E-DPCCH, and transmits userdata for the mobile station UE based on the control data for the EULtransmitted through the E-DPCCH.

The DPCCH transmits control data such as a pilot symbol that is used forRAKE combining, SIR measurement, or the like, a Transport FormatCombination Indicator (TFCI) for identifying a transmission format ofuplink DPDCH, and a downlink power control bit in a downlink.

In addition, the DPDCH is paired with the DPCCH, and transmits user datafor the mobile station UE based on the control data transmitted throughthe DPCCH. However, if user data that should be transmitted does notexist in the mobile station UE, the DPDCH can be configured not to betransmitted.

In addition, in the uplink, a “High Speed Dedicated Physical ControlChannel (HS-DPCCH)” and a “Random Access Channel (RACH)”, which areneeded when the HSPDA is applied, are also used.

The HS-DPCCH transmits a Channel Quality Indicator (CQI) in a downlinkand an acknowledge signal (Ack or Nack) for the HS-DPCCH.

As shown in FIG. 5, the mobile station UE according to this embodimentis provided with a bus interface 31, a call processing section 32, abaseband processing section 33, a radio frequency (RF) section 34, and atransmission-reception antenna 35.

However, these functions can be independently present as hardware, andcan be partly or entirely integrated, or can be configured through aprocess of software.

The bus interface 31 is configured to forward user data output from thecall processing section 32 to another functional section (for example,an application related functional section). In addition, the businterface 31 is configured to forward user data transmitted from anotherfunctional section (for example, the application related functionalsection) to the call processing section 32.

The call processing section 32 is configured to perform a call controlprocessing for transmitting and receiving user data.

The baseband signal processing section 33 is configured to transmit, tothe call processing section 32, the user data acquired by performing,against the baseband signals transmitted from the RF section 34, a Layer1 processing including a despreading processing, a RAKE combiningprocessing, and an “Forward Error Correction (FEC)” decode processing, a“Media Access Control (MAC)” processing including a MAC-e processing anda MAC-d processing, and a “Radio Link Control (RLC)” processing.

In addition, the baseband signal processing section 33 is configured togenerate the baseband signals by performing the RLC processing, the MACprocessing, or the layer-1 processing against the user data transmittedfrom the call processing section 32 so as to transmit the basebandsignals to the RF section 34.

Detailed description of the functions of the baseband signal processingsection 33 will be given later.

The RF section 34 is configured to generate baseband signals byperforming the detection processing, the filtering processing, thequantization processing, or the like against radio frequency signalsreceived through the transmission-reception antenna 35, so as totransmit the generated baseband signals to the baseband signalprocessing section 33.

In addition, the RF section 34 is configured to convert the basebandsignals transmitted from the baseband signal processing section 33 tothe radio frequency signals.

As shown in FIG. 6, the baseband signal processing section 33 isprovided with a RLC processing section 33 a, a MAC-d processing section33 b, a MAC-e processing section 33 c, and a layer-1 processing section33 d.

The RLC processing section 33 a is configured to transmit, to the MAC-dprocessing section 33 b, the user data transmitted from the callprocessing section 32 by performing a processing (RLC processing) in anupper layer of a layer-2 against the user data.

The MAC-d processing section 33 b is configured to grant a channelidentifier header, and to create a transmission format in the uplinkbased on the limitation of transmission power.

As shown in FIG. 7, the MAC-e processing section 33 c is provided withan Enhanced Transport Format Combination (E-TFC) selecting section 33 c1 and an HARQ processing section 33 c 2.

The E-TFC selecting section 33 c 1 is configured to determine atransmission format (E-TFC) of the E-DPDCH and the E-DPCCH, based onscheduling signals transmitted from the radio base station Node B.

In other words, the E-TFC selecting section 33 c 1 is configured todetermine a transmission rate of user data in uplink.

In addition, the E-TFC selecting section 33 c 1 is configured totransmit transmission format information on the determined transmissionformat (that is, a transmission data block size, an transmission powerratio between the E-DPDCH and the DPCCH, or the like) to the layer-1processing section 33 d, and also to transmit the determinedtransmission data block size or transmission power ratio to the HARQprocessing section 33 c 2.

Here, the scheduling signals include the maximum allowable transmissionrate of user data in the mobile station UE (for example, a maximum valueof the transmission power ratio between the E-DPDCH and the DPCCH(maximum allowable transmission power ratio), or the like), or aparameter related to the maximum allowable transmission rate.

In this description, unless specified otherwise, it is assumed that themaximum allowable transmission rate includes the parameter related tothe maximum allowable transmission rate.

Such scheduling signals are information that is signaled in the cellwhere the mobile station UE is located, and includes control informationfor all the mobile stations located in the sector, or a specific groupof the mobile stations located in the sector.

Here, the E-TFC selecting section 33 c 1 is configured to increase thetransmission rate of user data in the uplink up to the maximum allowabletransmission rate notified by the scheduling signals from the radio basestation Node B.

Specifically, the E-TFC selecting section 33 c 1 may be configured toincrease the transmission rate of the uplink user data up to the initialmaximum allowable transmission rate notified from the radio networkcontroller RNC automatically, while the serving cell is being changed.

More Specifically, the E-TFC selecting section 33 c 1 is configured todetermine the transmission rate of the uplink user data based on themaximum allowable transmission rate notified by the scheduling signalsfrom the radio base station NodeB.

In addition, the E-TFC selecting section 33 c 1 may be configured toincrease the transmission rate of uplink user data up to the maximumallowable transmission rate signaled by the changed serving cell of themobile station (destination cell) automatically, after the serving cellhas been changed.

More specifically, the E-TFC selecting section 33 c 1 may be configuredto determine the transmission rate of uplink user data based on themaximum allowable transmission rate signaled by the changed serving cellof the mobile station UE (destination cell), after the serving cell hasbeen changed.

In addition, the E-TFC selecting section 33 c 1 may be configured toincrease the transmission rate of uplink user data up to the maximumallowable transmission rate notified by the radio network controller RNCautomatically, after the serving cell has been changed.

More specifically, the E-TFC selecting section 33 c 1 may be configuredto determine the transmission rate of uplink user data based on themaximum allowable transmission rate notified by the radio networkcontroller RNC, after the serving cell has been changed.

The HARQ processing section 33 c 2 is configured to perform processcontrol for the “stop-and-wait of N-process”, so as to transmit the userdata in the uplink based on an acknowledge signal (Ack/Nack for uplinkdata) transmitted from the radio base station Node B.

Specifically, the HARQ processing section 33 c 2 is configured todetermine whether or not the receive processing of downlink user datahas been successful based on the result of the “Cyclic Redundancy Check(CRC)” entered from the first layer processing section 33 d.

Then, the HARQ processing section 33 c 2 is configured to generate anacknowledge signal (Ack/Nack for downlink user data) based on thedetermined result, so as to transmit the acknowledge signal to thelayer-1 processing section 33 d.

In addition, the HARQ processing section 33 c 2 is configured totransmit, to the MAC-d processing 33 d, the downlink user data enteredfrom the layer-1 processing section 33 d when the above-describeddetermination result has been successful.

As shown in FIG. 8, the radio base station Node B according to thisembodiment is provided with an HWY interface 11, a baseband signalprocessing section 12, a call control section 13, at least onetransmitter-receiver section 14, at least one amplifier section 15, andat least one transmission - reception antenna 16.

The HVY interface 11 is an interface for a radio network controller RNC.Specifically, the HWY interface 11 is configured to receive user datatransmitted from the radio network controller RNC to a mobile station UEvia a downlink, so as to enter the user data to the baseband signalprocessing section 12.

In addition, the HWY interface 11 is configured to receive control datafor the radio base station Node B from the radio network controller RNC,so as to enter the received control data to the call control section 13.

In addition, the HWY interface 11 is configured to acquire, from thebaseband signal processing section 12, the user data included in theuplink signals which are transmitted from a mobile station UE via anuplink, so as to transmit the acquired user data to the radio networkcontroller RNC.

Further, the HWY interface 11 is configured to acquire the control datafor the radio network controller RNC from the call control section 13,so as to transmit the acquired control data to the radio networkcontroller RNC.

The baseband signal processing section 12 is configured to generatebaseband signals by performing the RLC processing, the MAC processing(the MAC-d processing and the MAC-e processing), or the layer-1processing against the user data acquired from the HWY interface 11, soas to forward the generated baseband signals to the transmitter-receiversection 14.

Here, the MAC processing in the downlink includes an HARQ processing, ascheduling processing, a transmission rate control processing, or thelike.

In addition, the layer-1 processing includes a channel coding processingof user data, a spreading processing, or the like.

In addition, the baseband signal processing section 12 is configured toextract user data by performing the layer-1 processing, the MACprocessing (the MAC-e processing and the MAC-d processing), or the RLCprocessing against the baseband signals acquired from thetransmitter-receiver section 14, so as to forward the extracted userdata to the HWY interface 11.

Here, the MAC processing in the uplink includes the HARQ processing, thescheduling processing, the transmission rate control processing, aheader disposal processing, or the like.

In addition, the layer-1 processing in the uplink includes thedespreading processing, the RAKE combining processing, the errorcorrection decode processing, or the like.

Detailed description of the functions of the baseband signal processingsection 12 will be given later.

In addition, the call control section 13 is configured to perform thecall control processing, based on the control data acquired from the HWYinterface 11.

The transmitter-receiver section 14 is configured to perform processingof converting baseband signals, which are acquired from the basebandsignal processing section 12, to radio frequency signals (downlinksignals), so as to transmit the converted radio frequency signals to theamplifier section 15.

In addition, the transmitter-receiver 14 is configured to performprocessing of converting the radio frequency signals (uplink signals),which are acquired from the amplifier section 15, to the basebandsignals, so as to transmit the converted baseband signals to thebaseband signal processing section 12.

The amplifier section 15 is configured to amplify the downlink signalsacquired from the transmitter-receiver section 14, so as to transmit theamplified downlink signals to the mobile station UE via thetransmission-reception antenna 16.

In addition, the amplifier 15 is configured to amplify the uplinksignals received by the transmission - reception antenna 16, so as totransmit the amplified uplink signals to the transmitter-receiversection 14.

As shown in FIG. 9, the baseband signal processing section 12 isprovided with a RLC processing section 121, a MAC-d processing section122, and a MAC-e and first layer processing section 123.

The MAC-e and layer-1 processing section 123 is configured to perform,against the baseband signals acquired from the transmitter-receiversection 14, the despreading processing, the RAKE combining processing,the error correction decode processing, the HARQ processing, or thelike.

The MAC-d processing section 122 is configured to perform a disposalprocessing of header against output signals from the MAC-e and layer-1processing section 123.

The RLC processing section 121 is configured to perform, against theoutput signals from the MAC-d processing section 122, the retransmissioncontrol processing in the RLC layer or the reestablishment processing ofRLC-Service Data Section (SDU).

However, these functions are not clearly divided per hardware, and canbe obtained by software.

As shown in FIG. 10, the MAC-e and layer-1 processing section(configuration for the uplink) 123 is provided with a DPCCH RAKE section123 a, a DPDCH RAKE section 123 b, an E-DPCCH RAKE section 123 c, anE-DPDCH RAKE section 123 d, an HS-DPCCH RAKE section 123 e, a RACHprocessing section 123 f, a Transport Format Combination Indicator(TFCI) decoder section 123 g, buffers 123 h and 123 m, re-despreadingsections 123 iand 123 n, FEC decoder sections 123 j and 123 p, anE-DPCCH decoder section 123 k, a MAC-e functional section 123 l, an HARQbuffer 123 o, a MAC-hs functional section 123 q, and an interferencepower measurement section 123 r.

The E-DPCCH RAKE section 123 c is configured to perform, against theE-DPCCH in the baseband signals transmitted from thetransmitter-receiver section 14, the despreading processing and the RAKEcombining processing using a pilot symbol included in the DPCCH.

The E-DPCCH decoder section 123 k is configured to acquire transmissionformat number related information, HARQ related information, schedulingrelated information, or the like, by performing the decode processingagainst the RAKE combining outputs of the E-DPCCH RAKE section 123 c, soas to enter the information to the MAC-e functional section 123 l.

The E-DPDCH RAKE section 123 d is configured to perform, against theE-DPDCH in the baseband signals transmitted from thetransmitter-receiver section 14, the despreading processing using thetransmission format information (the number of codes) transmitted fromthe MAC-e functional section 1231 and the RAKE combining processingusing the pilot symbol included in the DPCCH.

The buffer 123 m is configured to store the RAKE combining outputs ofthe E-DPDCH RAKE section 123 d based on the transmission formatinformation (the number of symbols) transmitted from the MAC-efunctional section 123 l.

The re-despreading section 123 n is configured to perform thedespreading processing against the RAKE combining outputs of the E-DPDCHRAKE section 123 m, based on the transmission format information(spreading factor) transmitted from the MAC-e functional section 123 l.

The HARQ buffer 123 o is configured to store the despreading processingoutputs of the re-despreading section 123 n, based on the transmissionformat information transmitted from the MAC-e functional section 123 l.

The FEC decoder section 123 p is configured to perform an errorcorrection decoding processing (the FEC decoding processing) against thedespreading processing outputs of the re-despreading section 123 n,which is stored in the HARQ buffer 123 o, based on the transmissionformat information (transmission data block size) transmitted from theMAC-e functional section 123 l.

The interference power measurement section 123 r is configured tomeasure an interference volume (noise rise) in the uplink such asinterference power by a mobile station UE whose cell serves as aservicing cell, and the entire interference power.

Here, the noise rise is a ratio between the interference power in apredetermined channel within a predetermined frequency and noise power(thermal noise power or noise power from the outside of the mobilecommunication system) within the predetermined frequency (i.e., areceiving level from a noise floor).

In other words, the noise rise is a received interference power offsetthat a receiving level in communication has against a receiving level(noise floor) in non-communication.

The MAC-e functional section 123 l is configured to calculate and outputthe transmission format information (the number of codes, the number ofsymbols, spreading factor, transmission data block size, and the like)based on the transmission format number related information, the HARQrelated information, the scheduling related information, and the like,which are acquired from the E-DPCCH decoder section 123 k.

In addition, as shown in FIG. 11, the MAC-e functional section 123 l isprovided with a receive processing command section 123 l 1, an HARQprocessing section 123 l 2, and a scheduling section 123 l 3.

The receive processing command section 123 l 1 is configured to transmitthe transmission format number related information, the HARQ relatedinformation, and the scheduling related information, which are enteredfrom the E-DPCCH decoder section 123, to the HARQ processing section 123l 2.

In addition, the receive processing command section 123 l 1 isconfigured to transmit, to the scheduling section 123 l 3, thescheduling related information entered from the E-DPCCH decoder 123 k.

Further, the receive processing command section 123 l 1 is configured tooutput the transmission format information corresponding to thetransmission format number entered from the E-DPCCH decoder section 123k.

The HARQ processing section 123 l 2 is configured to determine whetheror not the receive processing of uplink user data has been successful,based on the CRC result entered from the FEC decoder section 123 p.

Then, the HARQ processing section 123 l 2 is configured to generate anacknowledge signal (Ack or Nack), based on the determination result, soas to transmit the generated acknowledge signal to the configuration forthe downlink of the baseband signal processing section 12.

In addition, the HARQ processing section 123 l 2 is configured totransmit the uplink user data entered from the FEC decoder section 123 pto the radio network controller RNC, when the above determination resulthas been successful.

In addition, the HARQ processing section 123 l 2 is configured to clearsoft decision values stored in the HARQ buffer 123 o, when the abovedetermination result has been successful.

On the other hand, the HARQ processing section 123 l 2 is configured tostore, in the HARQ buffer 123 o, the uplink user data, when the abovedetermination result has not been successful.

In addition, the HARQ processing section 123 l 2 is configured toforward the above determination result to the receive processing commandsection 123 l 1.

The receive processing control command section 123 l 1 is configured tonotify the E-DPDCH RAKE section 123 d and the buffer 123 m of anhardware resource that should be prepared for the following transmissiontime interval (TTI), so as to perform notification for reserving theresource in the HARQ buffer 123 o.

In addition, when the uplink user data is stored in the buffer 123 m,the receive processing command section 123 l 1 is configured to instructthe HARQ buffer 123 o and the FEC decoder section 123 p to perform theFEC decoding processing after adding the uplink user data, which isstored in the HARQ buffer 123 o, in a process corresponding to the TTIand a newly received uplink user data, per TTI.

In addition, the scheduling section 123 l 3 is configured to instructthe configuration for the downlink of the baseband signal processingsection 12 to transmit the scheduling signals including the maximumallowable transmission rate (maximum allowable transmission data blocksize, maximum allowable transmission power ratio, or the like), based onradio resources in the uplink of the radio base station Node B,interference volume (noise rise) in the uplink, or the like.

Specifically, the scheduling section 123 l 3 is configured to determinethe maximum allowable transmission rate based on the scheduling relatedinformation (radio resources in the uplink) transmitted from the E-DPCCHdecoder section 123 k or the interference volume in the uplinktransmitted from the interference power measurement section 123 r, so asto control the transmission rate of user data in a communicating mobilestation in communication.

Detailed descriptions of a control method based on the hardwareresources and a control method based on the interference volume in theuplink will be given below.

In the control method based on the hardware resources, the schedulingsection 123 l 3 is configured to signal the maximum allowabletransmission rate through the AGCH to the mobile station UE connected toa cell under the control of the radio base station Node B.

When the transmission rate of user data in the mobile station UEconnected to the cell under the control of the radio base station Node Bincreases and the hardware resources becomes insufficient, thescheduling section 123 l 3 lowers the maximum allowable transmissionrate so that shortage of the hardware resources will not be caused.

On the other hand, when the hardware resources have spaces in such acase when the user data transmission in the mobile station UE connectedto the cell under the control of the radio base station Node B iscompleted, or the like, the scheduling section 123 l 3 again increasesthe maximum allowable transmission rate.

In addition, in the control method based on the interference volume inthe uplink, the scheduling section 123 l 3 is configured to signal themaximum allowable transmission rate through the AGCH to the mobilestation UE connected to the sector under the control of the radio basestation Node B.

When the transmission rate of user data in the mobile station UEconnected to the cell under the control of the radio base station Node Bincreases and the interference volume (for example, noise rise) in theuplink exceeds an allowable value (for example, maximum allowable noiserise), the scheduling section 123 l 3 lowers the maximum allowabletransmission rate so that the interference volume in the uplink can fallwithin a range of the allowable value (see, FIG. 3).

On the other hand, when the interference volume (for example, noiserise) in the uplink falls within the range of the allowable value (forexample, maximum allowable noise rise) and there is a space therein inthe case when the user data transmission in the mobile station UEconnected to the cell under the control of the radio base station Node Bis completed, or the like, the scheduling section 123 l 3 againincreases the maximum allowable transmission rate (see, FIG. 3).

The radio network controller RNC according to this embodiment is anapparatus located in an upper level of the radio base station Node B,and is configured to control radio communications between the radio basestation Node B and the mobile station UE.

As shown in FIG. 12, the radio network controller RNC according to thisembodiment is provided with an exchange interface 51, a Logical LinkControl (LLC) layer processing section 52, a MAC layer processingsection 53, a media signal processing section 54, a radio base stationinterface 55, and a call control section 56.

The exchange interface 51 is an interface with an exchange 1, and isconfigured to forward the downlink signals transmitted from the exchange1 to the LLC layer processing section 52, and to forward the uplinksignals transmitted from the LLC layer processing section 52 to theexchange 1.

The LLC layer processing section 52 is configured to perform an LLCsub-layer processing such as a synthesis processing of a header such asa sequence number or a trailer.

The LLC layer processing section 52 is also configured to transmit theuplink signals to the exchange interface 51 and to transmit the downlinksignals to the MAC layer processing section 53, after the LLC sub-layerprocessing is performed.

The MAC layer processing section 53 is configured to perform a MAC layerprocessing such as a priority control processing or a header grantingprocessing.

The MAC layer processing section 53 is also configured to transmit theuplink signals to the LLC layer processing section 52 and to transmitthe downlink signals to the radio base station interface 55 (or a mediasignal processing section 54), after the MAC layer processing isperformed.

The media signal processing section 54 is configured to perform a mediasignal processing against voice signals or real time image signals.

The media signal processing section 54 is also configured to transmitthe uplink signals to the MAC layer processing section 53 and totransmit the downlink signals to the radio base station interface 55,after the media signal processing is performed.

The radio base station interface 55 is an interface with the radio basestation Node B. The radio base station interface 55 is configured toforward the uplink signals transmitted from the radio base station NodeB to the MAC layer processing section 53 (or the media signal processingsection 54) and to forward the downlink signals transmitted from the MAClayer processing section 53 (or the media signal processing section 54)to the radio base station Node B.

The call control section 56 is configured to perform a radio resourcecontrol processing, a channel setup and open processing by the layer-3signaling, or the like.

Here, the radio resource control processing includes a call admissioncontrol processing, a handover processing, or the like.

Specifically, the call control section 56 is configured to determinewhether or not cell change is performed based on the measurement reportfrom the mobile station UE, the measurement report from the radio basestation NodeB or the like.

In addition, the call control section 56 is configured to notify aninitial maximum allowable transmission rate of the user data to themobile station UE which performs the cell change, based on theallocation state of resources in the destination cell in the cellchange, throughput in the uplink user data or the like, when a servingcell of the mobile station is to be changed.

In addition, the call control section 56 may be configured to notify amaximum allowable transmission rate of the user data to the mobilestation UE by including the maximum allowable transmission rate of thedestination cell in the cell change in a message indicating that thecell change is completed (a layer 3 message), after the cell change hasbeen completed.

(Operation of Mobile Communication System According to First Embodimentof the Present Invention)

Referring to FIG. 13, an operation of the mobile communication systemaccording to the first embodiment of the present invention is describedbelow. FIG. 13 shows a cell change in a case where a serving cell of themobile station UE is changed from a cell under a radio base stationNodeB#1 to a cell under a radio base station NodeB#2.

As shown in FIG. 13, in step S1001, the mobile station UE is connectedto the radio base station NodeB#1 to perform a communication by a userdata channel.

In step S1002, when a radio network controller RNC determines to startthe cell change, the radio network controller RNC transmits, to theradio base station NodeB#1, a connection change preparation requestinstructing to make preparations for changing a serving cell of themobile station UE.

In step S1003, the radio base station NodeB#1 makes the preparationcorresponding to the connection change preparation request, andtransmits, to the radio network controller RNC, a connection changepreparation response notifying that the preparations are completed.

In step S1004, the radio network controller RNC transmits, to the radiobase station NodeB#2, a connection change preparation requestinstructing to make preparations for changing the serving cell of themobile station UE.

In step S1005, the radio base station NodeB#2 makes preparationcorresponding to the connection change preparation request, andtransmits, to the radio network controller RNC, a connection changepreparation response notifying that the preparations are completed.

In step S1006, the radio network controller RNC transmits, to the radiobase station NodeB#1, a connection release request for releasing theconnection between the mobile station UE and the radio base stationNodeB#1.

In steps S1007 and S1008, the radio network controller RNC transmits, tothe radio base station NodeB#2 and the mobile station UE, a connectionsetup request for setting the connection between the mobile station UEand the radio base station NodeB#2.

Here, the radio network controller RNC reports the initial maximumallowable transmission rate of uplink user data to the mobile station UEwith using the connection setup request.

In step S1009, the radio network controller RNC receives an uplinksynchronization establishment response from the radio base stationNodeB#2 including the destination serving cell in the cell change.

In step S1010, the radio network controller RNC receives a downlinksynchronization establishment response from the mobile station UE whichperforms the cell change.

In step S1011, the radio network controller RNC notifies the mobilestation UE of the maximum allowable transmission rate of the uplink userdata signaled by the destination serving cell in the cell change withusing the completion message (layer 3 message) for notifying that thecell change is completed.

In step S1012, a communication by the user data channel set between themobile station UE and the radio base station NodeB#2 is started.Thereafter, until the mobile station UE receives the maximum allowabletransmission rate of the new uplink user data from the destinationserving cell via the absolute grant allocation channel, the mobilestation UE automatically increases the transmission rate of the uplinkuser data up to the notified maximum allowable transmission rate of theuplink user data.

(Effect and Advantage of Mobile Communication System According to FirstEmbodiment of the Present Invention)

According to the mobile communication system in the case of the firstembodiment of the present invention, even when the cell change isperformed, the significant deterioration in communication qualityattributable to the shortage of resource allocation in the destinationcell can be prevented.

INDUSTRIAL APPLICABILITY

As described above, the present invention can provide a transmissionrate control method, a mobile station and a radio network controllerwhich can prevent significant deterioration in communication qualityattributable to the shortage of resource allocation in a destinationcell, even when cell change is performed.

1. A transmission rate control method for controlling a transmissionrate of user data to be transmitted via an uplink by a mobile station,the method comprising the steps of: notifying, at a radio networkcontroller, an initial maximum allowable transmission rate of the userdata to the mobile station, when a serving cell of the mobile station isto be changed; determining, at the mobile station, the transmission rateof the user data based on the initial maximum allowable transmissionrate notified from the radio network controller; and determining, at themobile station, the transmission rate of the user data based on amaximum allowable transmission rate notified from the changed servingcell of the mobile station, after the maximum allowable transmissionrate is received at the mobile station.
 2. The transmission rate controlmethod according to claim 1, comprising the step of signaling, at thechanged serving cell of the mobile station, the maximum allowabletransmission rate in the changed serving cell of the mobile station tothe mobile station; and wherein the mobile station determines thetransmission rate of the user data based on the signaled maximumallowable transmission rate, after the maximum allowable transmissionrate is signaled to the mobile station.
 3. The transmission rate controlmethod according to claim 1, comprising the step of notifying, at theradio network controller, the maximum allowable transmission rate in thechanged serving cell of the mobile station to the mobile station, withusing a layer-3 message; and wherein the mobile station determines thetransmission rate of the user data based on the notified maximumallowable transmission rate, after the maximum allowable transmissionrate is notified to the mobile station.
 4. A mobile station whichtransmits user data via an uplink, comprising: an initial maximumallowable transmission rate receiving unit configured to receive aninitial maximum allowable transmission rate of the user data notified bya radio network controller, when a serving cell of the mobile station isto be changed; and a transmission rate control unit configured todetermine a transmission rate of the user data based on the initialmaximum allowable transmission rate notified from the radio networkcontroller, and to determine the transmission rate of the user databased on a maximum allowable transmission rate notified from the changedserving cell of the mobile station, after the maximum allowabletransmission rate is received.
 5. The mobile station according to claim4, comprising a maximum allowable transmission rate receiving unitconfigured to receive the maximum allowable transmission rate in thechanged serving cell of the mobile station signaled by the changedserving cell of the mobile station; and wherein the transmission ratecontrol unit is configured to determine the transmission rate of theuser data based on the received maximum allowable transmission rate. 6.The mobile station according to claim 4, comprising a maximum allowabletransmission rate receiving unit configured to receive the maximumallowable transmission rate in the changed serving cell of the mobilestation notified by the radio network controller; and wherein thetransmission rate control unit is configured to determine thetransmission rate of the user data based on the received maximumallowable transmission rate.